Clear coatings are commonly applied to printed matter to improve its appearance, as well as to protect it from scuffs, scratches, moisture, high temperatures, etc. Varnish, aqueous and ultraviolet (UV) coatings, for instance, are widely used in commercial printing. These clear coatings may be applied to an entire page to enhance and protect the page or can be applied to selected sections of the page to draw attention to those sections. Alternatively, lamination may be applied in some cases instead of coating, but serves the same purpose. These coatings or laminations are available in a range of gloss levels, from very glossy to very matte.
The clear coat finishes may change the color of the underlying printed image. For example, glossy finishes typically provide a significant increase in image chroma. This may be a very desirable outcome, and is, in many cases, the main reason for choosing to apply the coating despite the increased cost. However, this color change may be a problem for accurate color rendition.
Inline color measurements are typically made of prints to ensure accurate color rendition. For example, an inline spectrophotometer (ILS) may be located at the output end of a color digital printing presses, such as the Xerox Corp. iGen4®, to automate creation of destination profiles, spot color recipe selection, etc.
Coating or laminating systems may be fabricated or provided by after-market or third-party suppliers that are used inline or offline with the color presses. Since the coating or laminating may significantly alter the appearance of the color of the prints output by the press, the ability of the press to deliver accurate color to coated prints may be compromised. This is because the prints are altered by the coating prints after the prints have been sensed by the ILS.
Moreover, many print shops may not have their own coating and laminating equipment, and may have that work performed by a different shop. As a result, color adjustments have to be made well before the prints are coated, for instance, a day or two later, and therefore cannot properly correct for color inconsistency.
This may result in a failure to meet customers' color requirements, especially when images include specific spot colors, such as logo colors or user-defined colors.
U.S. patent application Ser. No. 12/143,030, herein incorporated by reference in its entirety, discloses an apparatus and method for controlling the color of clear coated images on media. The apparatus may include a sensor configured to measure color attributes of the clear coated image and to provide color information of the clear coated image. The controller can be configured to determine a difference between the color information of the clear coated image and the reference color information, and can adjust the image output settings according to the difference between the color information and the reference color information to achieve adjusted image output settings.
Also U.S. patent application Ser. No. 12/274,846, herein incorporated by reference in its entirety, discloses a system and method for generating a destination printer profile for coated images using measured color attributes associated with the printed and coated color patches and modifying the initial printer profile for the target colors as a function of the error to generate a new destination printer profile to produce the desired color after coating the printed images.
In both of these applications, it is necessary to measure the color of the printed samples after coating. As discussed above, this is often not feasible in practice.